The Crónica Latina records that “la huerfana doña Mayor, hija del…conde Sancho” married “al rey de Navarra y Nájera Sancho, nieto de Sancho Abarca”. She and her husband confirmed the rights of the Abbey of San Millán 24 Jun 1011. "Sancius…rex" recommended the rule of St Benedict to the monastery of Leire by charter dated 21 Oct 1022, subscribed by "Eximina regina mater regis, Regina domna Muma, Garsia et Ranimirus, Gundesalbus et Fernandus". "Sancius rex et uxor mea Muma dompna regina" donated property to the monastery of Yarte y Anoz by charter dated 17 May 1024.
She succeeded her brother in 1029 as Condesa de Castilla. "Domna Major regina" confirmed a charter of "Sancius Hispaniarum rex" dated 26 Jun 1033 which related to concessions to the monastery of Oriense. "Sancius…rex…cum coniuge mea regina domina Maiora" donated the monastery of San Sebastian to the monastery of Leire by charter dated 17 Apr 1014, redated to .
She became a nun after her the death of her husband. She founded the monastery of San Martín de Fromista 13 Jul 1066, the document naming her father but not her husband. The testament of "Maior regina Christi ancilla", in which she requests burial in the monastery of San Martín de Frómista, is dated 13 Jun 1066. 1